Tessellated electromechanical transducer element



y 1963 F. MASSA 3,090,939

TESSELLATED ELECTROMECHANICAL TRANSDUCER ELEMENT Filed May 13, 1955 F IG. 1

INVENTOR.

FRANK MASSA United StatesPatent O TESSELLATED ELECTROMECHANICAL TRANS- DUCER ELEMENT 3 Frank Massa, Cohasset, Mass, assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed May 13, 1953, Ser. No. 354,862 2 Claims. (Cl. 340-9) This invention concerns a novel electromechanical transducer element for a hydrophone.

An object of the invention is to provide a novel trans ducer element for a hydrophone.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a view predominantly in section of a hydrophone including an electromechanical transducer element in accordance with this invention,

FIG. 2 is a plan view of a dual electromechanical transducer element in accordance with this invention, and

FIG. 3 is a schematic diagram showing the electrical system of the hydrophone shown in FIG. 1.

There is shown in FIG. 1 a housing 2 having a ring 3 that holds in place a rubber diaphragm 4. Seated in housing 2 is an electromechanical transducer element 5 of disc-shape isolated against transfer of mechanical vibration on its bottom face by a layer 7 of Corprene and at its periphery by a layer 8 of Corprene. Corprene is a material described in U.S. Patent 2,529,648, column 3, lines 27-29, et seq.

An electromechanical transducer element 5 suitable for the hydrophone shown in FIG. 1 comprises a circular disc 9 that is made up of a hexagonal plate 10 surrounded by six plates 11. An embodiment in accordance with this invention may be about 1% inches diameter and about /2 inch thick. The circular disc 9 is made by assembling initially about hexagonal plate 10 a series of six similar hexagonal plates 12 to form a tessellated pattern, the six plates 12 being bonded to the central hexagonal plate 10 and to each other by a thin layer 13 of Corprene. The composite assembly is then cut down to a circular contour to provide disc 9. In the resulting combination, the peripheral plates 12 each have three adjoining hexagonal sides and an arcuate side joining the ends of two of its hexagonal sides and whose radius is approximately twice the length of one of said hexagonal sides. The individual plates 10, 12 are cut from an extruded bar of barium titanate so as to be substantially identical to each other in transducing properties and the assembly fabricated from a group of selected elements which show a variation in piezoelectric sensitivity not in excess of plus or minus three per cent. Effectively, therefore, element 5 consists of a 1% inch diameter disc 9 subdivided into seven isolated smaller parts including a central hexagonal plate 10 surrounded by six plates 11. The isolation of the plates 11 serves to prevent undesirable transverse resonance modes.

A conductive pin 14 (FIG. 1) extends axially from the rear of element 5 through an axial insulating tubing 15 in housing 2 and conducting pin 14 extends externally of housing 2 in a direction away from element 5. A conducting pin 16 is anchored at one end in housing 2 and at its other end is connected to the front of element 5 and at the periphery thereof. Conducting pin 16 is imbedded in housing 2 to provide a minimum of contact resistance.

A pipe plug is tapped into an opening 18, in housing 2 and opening 18 is provided with a connecting port 19 that opens into the space in housing 2 at the front of ice y 4 element 5. Pipeplug can be removed for the purpose of filhng openings 18 and '19 and the space at the front rear periphery of housing-2. r

Disposed in the rear of housing25 are a pair of spaced discs 26 between which is a compressible gland 27. Discs 26 and gland 27 are assembled together by means of screws 28 and nuts 29 turned thereon.

Lining housing 25 is a tubular shock mount 31 of foam rubber. Nested in shock mount 31 is a preamplifier 33 including a tube 34 and a tube socket 35. A conductor 38 connects preamplifier 33 to conducting pin 16 through screw 39. A conductor 41 connects preamplifier 33 with the rear extremity of conducting pin 14. Conductors 42, 43 and 44 connect preamplifier 33 through a shielded cable 45 to other parts of the hydrophone circuit (not shown).

There are shown in FIG. 3 details of the electrical system of the hydrophone. The transducer element 5 is coupled to the triode tube 47 through a condenser 46. The plate supply of tube 47 is provided through lead 42 and the heater supply of the tube is provided through lead 43. The tube 47 is arranged to be self biased by connecting resistor 48 between the cathode 49 and the grid 50. The output is derived from the cathode side of the tube through a resistor 51 which output is coupled to lead 44 through a condenser 52. The shield 53 of the cable 45 serves as a common return path for both the plate supply and the heater supply of tube 47.

Each of the two transducing parts of the transducer displays a different directional pattern at a prescribed frequency of operation. These two individual patterns are combined electrically to result in an optimum overall directional characteristic.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. An electromechanical transducer element adapted for use in a hydrophone in connection with underwater sound systems, said element comprising a circular disc, said disc including a central hexagonal plate and six peripheral plates surrounding said central hexagonal plate, a thin layer of Corprene insulation disposed between matching faces of the plates included in said disc, each peripheral plate comprising a partial hexagon having three adjoining hexagonal sides of dimensions the same as the sides of said central hexagonal plate and an arcuate side joining the ends of two of its hexagonal sides and whose radius is approximately twice the length of one of said hexagonal sides, and said central and peripheral plates forming a tessellatcd pattern.

2. An electromechanical transducer element for use in a hydrophone in connection with underwater sound systems, said element comprising a circular disc of about 1% inches diameter and about V2 inch thickness, said disc including a central hexagonal plate of barium titanate and six peripheral plates of barium titanate surrounding said central hexagonal plate, a thin layer of Corprene insulation disposed between matching faces of the plates included in said disc, each peripheral plate comprising a partial hexagon having three adjoining hexagonal sides of dimensions the same as the sides of said central hexagonal plate and an arcuate side joining the ends of two of its hexagonal sides and whose radius is approximately twice the length of one of said hexagonal sides, and said Patented 'May 21, 1963 central and peripheral plates forming a tes sellated pattern.

References Cited in the file of this patent UNITED STATES PATENTS Williams Jan. 6, 1942 Batchelder Aug. 7, 1945 Pope Aug. 13, 1946 Benioif Sept. 3, 1946 Massa Dec. 31, 1946 4 Shaper May 23, 1950 Klein Sept. 5, 1950 Ma-ssa Sept. 5, 1950 Chess Aug. 14, 1951 Klein June 24, 1952 Smyth May 29, 1956 Camp et a1. June 25, 1957 Batchelder- July 22, 1958 FOREIGN PATENTS Great Britain Jan. 20, 1954 

1. AN ELECTROMECHANICAL TRANSDUCER ELEMENT ADAPTED FOR USE IN A HYDROPHONE IN CONNECTION WITH UNDERWATER SOUND SYSTEMS, SAID ELEMENT COMPRISING A CIRCULAR DISC, SAID DISC INCLUDING A CENTRAL HEXAGONAL PLATE AND SIX PERIPHERAL PLATES SURROUNDING SAID CENTRAL HEXAGONAL PLATE A THIN LAYER OF CORPRENE INSULATION DISPOSED BETWEEN MATCHING FACES OF THE PLATES INCLUDED IN SAID DISC, EACH PERIPHERAL PLATE COMPRISING A PARTIAL HEXAGON HAVING THREE ADJOINING HEXAGONAL SIDES OF DIMENSIONS AT THE SAME AS THE SIDES OF SAID CENTRAL HEXAGONAL PLATE AND AN ARCUATE SIDE JOINING THE ENDS OF TWO OF ITS HEXAGONAL SIDES AND WHOSE RADIUS IS APPROXIMATELY TWICE THE LENGTH OF ONE OF SAID HEXAGONAL SIDES, AND SAID CENTRAL AND PERIPHERAL PLATES FORMING A TESSELLATED PATTERN. 